The Greek alphabet is thought to be the ancestor of all major European alphabets today.
Although the script was adapted from the Semites around the tenth or ninth century BCE,
it included significant improvements which were directly responsible for its influence.
Among the improvements were the transformation of certain Semitic letters into vowels,
and the invention of new letters for sounds absent from Semitic languages.
Originally, just like the Semitic scripts, Greek was written from right to left but
following the sixth century BCE, it was already written from left to right and top to bottom.

The early script had many variations depending on the geographical region; the
two major subdivisions were the eastern and western ones. But in spite of the local
diversities, it gradually moved towards uniformity. A major event in this process
was when the Ionic alphabet of Miletus was officially adopted in Athens in 403 BCE.
Shortly after this, the rest of the mainland followed Athens's example and by the
middle of the fourth century BCE almost all local alphabets were unified,
establishing the classical twenty-four letter Greek script. In the middle of
the third century BCE, Aristophanes of Byzantium introduced the three accents,
acute, grave, and circumflex, in order to mark the tone or pitch of Greek words.